Spiral end mill and method of manufacturing the same

Abstract

A spiral end mill which can mill a substantially sharp inside corner of a work surface and attain a stable working accuracy for a long time. The spiral end mill has a hard sintered compact insert portion, a negative relief face a first circular land provided along the outer periphery of the insert portion, and a second circular land on the negative relief face so as to be continuous with the first circular land. The widths of the two circular lands may be the same as or different from each other, and the helix angle of a back line of the second circular land is less than that of the first circular land. A method of manufacturing the spiral end mill involves machining a relief angle in the outer periphery of the insert portion while changing the helix angle between the negative relief face and the rest of the outer periphery.

What is claimed is: 
     
       1. A spiral end mill having a hard sintered compact being arranged on an insert portion of said spiral end mill and a negative relief face having a chamfer for reducing the angle of an axial rake being provided on a forward end of said insert portion, said spiral end mill comprising: a first circular land portion being provided along an outer peripheral portion of said insert portion excluding said negative relief face to have a substantially constant first width; and   a second circular land portion, having a substantially constant second width, being provided on an outer peripheral portion of said negative relief face of said insert portion to be continuous with said first circular land portion;   wherein a helix angle of a line being defined by said second circular land portion and a peripheral flank is smaller than that of said first circular land portion; and   wherein said negative relief face has a width in the range of at least 0.05 mm and not more than 0.5 mm.   
     
     
       2. The spiral end mill in accordance with claim 1, wherein said first width of said first circular land portion is at least 0.01 mm and not more than 0.15 mm, and said second width of said second circular land portion is at least 0.01 mm and not more than 0.30 mm. 
     
     
       3. A spiral end mill comprising a tool body and a hard sintered compact insert bonded to said tool body, wherein said insert has a helical outer peripheral edge extending substantially along said insert, a forefront edge at a forward axial end of said insert, a negative relief face adjacent and interposed between said forefront edge and said outer peripheral edge, a first circular land having a substantially constant first width and extending adjacently along said helical outer peripheral edge, and a second circular land having a second width and extending adjacently along said negative relief face uninterrupted and continuous with said first circular land. 
     
     
       4. The spiral end mill in accordance with claim 3, wherein said insert further has a peripheral flank extending therealong adjacent said first circular land opposite said helical outer peripheral edge and adjacent said second circular land opposite said negative relief face, and wherein a line defined by an intersection of said second circular land with said peripheral flank extends at a helical angle less than a helix angle of said first circular land. 
     
     
       5. The spiral end mill in accordance with claim 3, wherein said insert further has a peripheral flank extending therealong adjacent said first circular land opposite said helical outer peripheral edge and adjacent said second circular land opposite said negative relief face, and wherein a first line defined by an intersection of said first circular land with said peripheral flank and extending at a first helical angle transitions smoothly through a curved line into a second line defined by an intersection of said second circular land with said peripheral flank and extending at a second helical angle less than said first helical angle. 
     
     
       6. The spiral end mill in accordance with claim 3, wherein said insert further has a peripheral flank extending therealong adjacent said first circular land opposite said helical outer peripheral edge and adjacent said second circular land opposite said negative relief face, wherein a first line defined by an intersection of said first circular land with said peripheral flank transitions abruptly at an intersection point into a second line defined by an intersection of said second circular land with said peripheral flank, and wherein said first and second lines respectively extend at first and second helical angles that are different from each other. 
     
     
       7. The spiral end mill in accordance with claim 6, wherein said second helical angle is of opposite helical direction relative to said first helical angle. 
     
     
       8. The spiral end mill in accordance with claim 3, wherein said negative relief face has a width in the range from 0.05 mm to 0.5 mm. 
     
     
       9. The spiral end mill in accordance with claim 8, wherein said width of said negative relief face is in the range from 0.1 mm to 0.4 mm. 
     
     
       10. The spiral end mill in accordance with claim 8, wherein said first width is in the range from 0.01 mm to 0.15 mm, and said second width is in the range from 0.01 mm to 0.3 mm. 
     
     
       11. The spiral end mill in accordance with claim 3, wherein said first width is in the range from 0.01 mm to 0.15 mm, and said second width is in the range from 0.01 mm to 0.3 mm. 
     
     
       12. The spiral end mill in accordance with claim 11, wherein said second width is greater than said first width. 
     
     
       13. The spiral end mill in accordance with claim 11, wherein said first and second widths are substantially equal. 
     
     
       14. The spiral end mill in accordance with claim 11, wherein said first width is not more than 0.1 mm. 
     
     
       15. The spiral end mill in accordance with claim 3, having an effective tool diameter that is substantially constant over said helical outer peripheral edge and said negative relief face. 
     
     
       16. The spiral end mill in accordance with claim 3, being so configured as to be able to mill a substantially sharp right angle inside corner in a workpiece along said forefront edge and said negative relief face. 
     
     
       17. The spiral end mill in accordance with claim 3, wherein said insert further has a peripheral flank extending therealong adjacent said first circular land opposite said helical outer peripheral edge and adjacent said second circular land opposite said negative relief face, wherein said peripheral flank is continuous and has a uniform helical configuration along said first circular land and said second circular land.